<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>天气案例_监视属性简写</title>
  <!-- 引入Vue -->
  <script type="text/javascript" src="../js/vue.js"></script>
</head>

<body>
  <!-- 准备好一个容器 -->
  <div id="root">
    <h2>今天天气很{{info}}</h2>
    <button @click="changeWeather">切换天气</button>

  </div>
</body>

<script type="text/javascript">

  new Vue({
    el: '#root',
    data: {
      isHot: true,
      numbers: {
        a: 1,
        b: 1
      }
    },
    computed: {
      info() {
        return this.isHot ? '炎热' : '凉爽'
      }
    },
    methods: {
      changeWeather() {
        this.isHot = !this.isHot
      }
    },
    watch: {
      // 正常写法
      /* isHot: {
        // immediate: true, //初始化时让handler调用一下
        //deep:true, //深度监视
        //handler什么时候调用？当isHot发生改变时
        handler(newValue, oldValue) {
          console.log('isHot被修改了', newValue, oldValue);
        }
      }, */

      //简写
      isHot(newValue, oldValue) {
        console.log('isHot被修改了', newValue, oldValue);

      }
    }
  })
</script>

</html>